Summary of Work: The primary purpose of the project on fertility is to develop methods for identifying reproductive hazards. Ultimately, we are working toward developing methods for studying reproductive hazards in small populations so that localized exposures can be evaluated. First, we have developed questionnaire methods for measuring fertility using data on time to pregnancy, the number of noncontracepting menstrual cycles required to conceive. This measure can be the focus of epidemiologic studies of fertility or can be integrated into epidemiologic studies of other diseases such as breast cancer. Data from female dentists is being examined to study the relationship between mercury and nitrous oxide exposures and female reproduction. Data on fertility are also being collected in the Agricultural Health Study. These data will be available for an analysis of pesticide related effects and fertility in the fall of 1997. Our second approach focusses on developing biological markers of impaired ovarian function. We have begun by examining urinary metabolites of estrogen and progesterone. These have been measured in daily urine specimens from over 700 menstrual cycles from about 200 women. First, we developed a method for detecting day of ovulation using these urinary hormone data. Our ability to detect ovulation using this method was very good. Now we are developing methods for characterizing follicular development, luteal function, and hormonal factors associated with conception and pregnancy loss.